Radon in the spas of Croatia V. Radolic´ a , B. Vukovic´ a , G. S ˇ mit b , D. Stanic´ a , J. Planinic´ a, * a Department of Physics, University of Osijek, P.O. Box 144, 31000 Osijek, Croatia b Department of Chemistry, University of Osijek, P.O. Box 144, 31000 Osijek, Croatia Received 14 October 2004; received in revised form 21 January 2005; accepted 9 February 2005 Available online 31 May 2005 Abstract Radon concentrations in air and geothermal water of the spa pools in Croatia were measured and the average values of 40.3 and 4.5 kBq/m 3 were obtained, respectively. Great difference between radon concentrations in pool and spring water was considered as a result of mixing normal and geothermal water in the pool as well as the radon decay. Estimation of an effective dose, received by the personnel in the Bizovac spa, gave the value of 0.27 mSv/y. At the location Stubica, the transfer factor of the radon for air and thermal water in the pool was calculated, and the value of 4.9 G 0.7 ! 10 ÿ3 was obtained. Ó 2005 Published by Elsevier Ltd. Keywords: Radon concentration; Spa; Dose equivalent; Transfer factor 1. Introduction Radon ( 222 Rn) is a noble a-emitting radioactive gas produced by the decay of radium ( 226 Ra), and both are the members of uranium decay chain. The radon concentrations in soil gas due to continuous radium decay and different mechanisms of radon transport could be very high, with values up to several thousands Bq/m 3 * Corresponding author. Tel.: C385 31 211400; fax: C385 31 212514. E-mail address: planinic@pedos.hr (J. Planinic´). 0265-931X/$ - see front matter Ó 2005 Published by Elsevier Ltd. doi:10.1016/j.jenvrad.2005.02.016 Journal of Environmental Radioactivity 83 (2005) 191e198 www.elsevier.com/locate/jenvrad